DESIGN West: MEMS switch shrinks footprint

SAN JOSE, Calif.—The world's smallest magnetic reed switch was fabricated using micro-electro-mechanical system (MEMS) process technology, according to its designers Coto Technology Inc., who announced the switch Wednesday (April 23) at DESIGN West 2013 here.

MEMS radio-frequency (RF) switches have been announced before by startups like the now defunct Teravicta Technologies Inc. (Austin, Texas) for markets demanding RF operation, but those companies have failed to deliver on the promise. In contrast, Coto's 90-years of experience manufacturing traditional reed switches, and their focus on emerging markets instead of RF, give them a stronger chance of success, according to Stephen Day, Coto's vice president of technology,.

"We've combined our deep expertise in making glass-tube mechanical reed switches, with high aspect ratio [HARM] fabrication techniques to create a switch with higher reliability connections, with more force than the MEMS switches of the past," Day said. "Traditional MEMS switches are small, but can't handle the high power required by many applications."

The RedRock RS-A-2515 MEMS-based magnetic reed switch requires just 300 milliWatts to switch, and zero power to maintain its position after switching. The hot-swappable part can be switched by a magnetic field of less than 25 milliTeslas, but is highly directional, making it virtually immune to stray magnetic fields, according to Coto. The switch can handle up to 100 volts DC with a switching current of 50 milliAmps DC or 35 milliAmps AC.

Coto Technologies RedRock magnetic reed switch is fabricated using micro-electro-mechanical system (MEMS) manufacturing techniques to make it the world's smallest single-pole, single throw (SPST) switch.

Coto's traditional glass-tube magnetic reed switches are available today in sizes as small as five millimeter, but by going to a MEMS fabrication process—HARM—that enables its switches to measure just 2-by-1 millimeter, it hopes to attract design wins from makers of small mobile devices that must subsist on battery power. The MEMS process also offers increased item-to-item uniformity when compared to traditional reed switches.

The hermetically sealed package, using wafer scale packaging and MEMS economies of scale, will enable its price to continue to drop for mass market applications, as well as make it suitable today for high-reliability medical, military, consumer and industrial applications of all kinds, according to Coto.